1. Field of the Invention
The present invention relates to an image display device and particularly to an image display device that presents an image based on image display light to a user as a virtual image.
2. Description of the Related Art
In recent years, so-called head up displays that use LEDs or semiconductor laser light sources have been developed as image display devices. These head up displays include those that use screens for imaging a real image that corresponds to an image recognized as a virtual image by a user via a windshield of a vehicle (e.g., patent document No. 1). These screen include two types of screens: a reflection type screen provided with a reflection surface; and a transmission type screen provided with a transparent surface.
[Patent document No. 1] JP 2003-127707
In these head up displays, the screens are often used to widen the viewing angle of a video image by diffusing video light projected from a projection lens. These screens are formed from various materials, and the optical performance may be degraded due to changes over time depending on the materials.
Also, by changing the materials used for forming the screens, the optical properties of the screens such as viewing angles or the like can be changed. Therefore, there is a need for a technology that allows for the minimization of the number of components, easy assembly, and inexpensive manufacturing as well as a technology that facilitates the replacement of a screen such as the replacement of a screen according to the preference of the user, the replacement of a screen having reduced performance with a new screen, and the like.